Chemical heating pad, particularly useful in permanent waving of human hair



F HUMAN HAIR 19 PAD, PARTICULARLY USEFUL IN PERMANENT WAVIN Filed April25 46 Dec. 12, 1950 M. J. ROOT ETAL CHEMICAL HEATING G 2/ rrr INVENTORSPatented Dec. 12, 1950 UNITED STATES PATENT OFFICE CHEMICAL HEATING PAD,PARTICULARLY USEFUL IN PERMANENT WAVING OF HUMAN HAIR Application April23, 1946, Serial No. 664,193

This invention relates to chemical heating pads and particularly to padsadapted for use in p rmanent waving of human hair.

Primary objects of this invention are to provide a chemical heating padwhich will eliminate operation hazards, minimize likelihood of scalpburns. and which will give more uniform heating results and be morefoolproof in the sense that failure of operators to follow preciseinstructions will not necessarily prevent generation of temperaturessufllciently elevated and of suflicient duration to accomplish thedesigned purpose of the pad in use. A further object of the invention isto provide a pad which may be properly activated and applied to thetress with fewer manual operations, thus saving time in the wavingoperation. A further object of the invention is to provide a pad whichmay be properly'acjtivated by a simple operation of dipping in anactivating so1u- 'tion.

Chemical heating pads have fallen into two general groups: those withperforate and those with imperforate working surfaces. The perforatetype, for example pads comprising envelopes having perforated foil orpaperwalls for the working surface. have the marked drawback ofmessiness, During handling the contents tend to sift through theperforations ontolthe outside of the pad and thence to the hands of theoperator, to the hair or elsewhere. Significant amounts of containedchemicals may thus be lost during shipment and handling. so that theremaining amount may become less than that necessary to develop thedesigned operating heat. The per forations are also objectionable fromthe standpoint of providing paths of too easy escape for steam developedinternally of the envelope after I 3 Claims. (Cl. 132-362) tion ofmoistening the contents then becomes a very important operation. Usuallythis operation involves application of an absorbent fabric such asflannel, saturatedwith the activating solution. must always an aqueoussolution, to th thin imperforate working face, and working the solutionfrom the flannel with the fingers through the imperforate but waterpermeable working face. To prevent the face from disintegrating duringthis physical manipulation it must have considerable wet tensilestrength, and this characteristic mereiy accentuates the difficulty offorcing the solution through the face. ingress of an amount of solutionsufficient for proper activation or the chemical is thus whollydependent upon the operators care and patience. If the operatorcarelessly shortens the time or amount of manipula tion, only heat ofinadequate temperature or duration may develop with resultingunsatisfactory performance.

A further defect of-present-day imperforate pads is that their workingfaces tend to hold the solution in their pores so that the pad often"water wings when the steam is internally gen erated, ballooning thepad, disturbing its placed relation on the tress, and sometimes causing,because the pad is clamped to the coiled tress, sud denpuncture, of aweak spot in the envelope releasing an uncontrolled and concentrated.mass of steam with almost explosive force accompanied by discharge ofthe contained chemicals. These minor explosions are obviously highlydangerous.

Chemical heating pads of this invention in their preferred form areprovided with working faces of unwoven, felted cellulosic fibers whichhave such high absorbency value and thickness that they are capable ofpractically instantaneously absorbing an amount of activating solutionmore than sufllcient to activate the contained chemicals to the desiredextent, and have porosities which avoid the water wing effect. If somemanipulation is contemplated, adequate strength may be provided byreinforcing the porous face with reticulated fabric or the like. As thusconstructed, by merely dipping the pad into the solution, the workingsurface will pick up in a very short period of time more than therequired amount of solution. and rapidly transfer to the contents, withlittle or no manipulation, an amount of that solution adequate forsatisfactory activation. With a pad that can thus absorb and transferall the solution necessary, it is not essential that the working facehave the wet-strength to withstand the extensive manipulation necessaryto force solution from an extraneous absorbent through a face that doesnot hold all the solution necessary, and accordingly the working facecan have a porosity in ranges wholly impractical where'extensivemanipulation is contemplated. Thus the porosityof absorbent materialworking-faces of this invention may be just short of that necessary toprevent sifting of the chemical and in such ranges of porosity that the"water wing eifect is not present.

Typical chemical heating pads of this invention are shown in theaccompanying drawings, in which Fig. 1 is a face view of one formofchemical heating pad of this invention;

Fig. 2 is a back view of the pad shown in Fig. 1;

Fig. 3 is a section taken along the line 3-3 of Fig. 1;

Fig. 4 is a face view of a modified form of ing pad embodying theinvention; and

Fig. 5 is an enlarged sectional view diagrammatically showing the pad ofFig. 4 positioned over a coiled tress during the waving operation.

As shown in the drawings, the pad of Figs. 1 to 3 comprises an. envelopehaving a front wall 2 formed of an imperforate, absorbent materialpervious to moisture, and having a back wall of an impervious material3. These two materials are sealed at their edges. by a heat sealingthermoplastic resin adhesive, indicated by the reference 5'. SealedWithin the envelope is the desired amount of exothermic composition 6.

The back material is preferably non-absorbent metal foil such asaluminum foil, 1 mil thick, although other suitable materials areparchment paper, resinrtreated paper, or metal foil laminated to paper.Preferably, the back wall should be of sufiioient thickness and/or ofsuch nature that it will have sufficient moldability to hold the pad inposition about the tress of the hair, though this is not essential.

The exothermic composition 6 may be anyone of the chemicals commonlyused, in chemical heating pads and which are activated upon applicationof water or some other solution to gen-- erate heat.

The adhesive 5 is of the heat-sealing type and can be applied either tothe back or face material or both, which may then be pressed together ata temperature above the softening, point of the resin withoutapplication of moisture and without activating Or disintegratin theenclosed exothermic composition. The seal is .efiected with cooling Thethermo-plastic resin should maintain the seal at the temperaturesnormally encountered. in machineless permanent. waving operations, i.e., from about 200 to 220 F., so that the pad will not separate duringthe waving op:- eration. We have found that resins of the polyvinyltype, especially vinyl chloride acetate copolymer resins havingsoftening points exceeding 212 F., are particularly suitable. Properlyplasticized cellulose derivative resins may also be used.

As is usual in heat-sealing, the edge may be flat or ridged in anymanner found to secure the most effective seal.

The face material is preferably essentially a cotton felt which may ormay not be reinforced by internal or external lamination or other as-.sembly with stranded fibers, such as an open heat- 4 mesh reticulatedgauze or other textile fabric. The thickness and kind of felt is suchthat when immersed in water at 70 F., for 10 seconds and allowed todrain for 10 seconds at 70 F., it retains an amount of absorbed water atleast equal to 0.2 grams per square inch, a suitable range being from0.20 to 1.00 gram per square inch. In addition to such water holdingcapacity, the felt has a porosity in the range which will prevent thewater wing effect. Since the porosity of suitable materials is veryhigh, standard methods of porosity test are not suffficiently accuratefor the purpose of definin the limits of suitable porosity for thepurposes of this invention. Ac-

cordingly A. S, T. M- air permeability test known under the tentativedesignation D 72643T is modified so that porosity is defined as theaverage number of seconds required for the displacement .of 400 ml. ofair through an area of one square inch of four thicknesses of thematerial. As thus measured, preferred felts of suitable porosity arethose having an air permeability value (porosity) of about 5 seconds asdetermined on a Gurley Densometer. These particular materials may have acaliper running between about 6 and about 15 mils and have a waterabsorbing capacity exceeding 0.2 grams per square inch.

In general, porosity as above defined is preferably within the range offrom 0.5 to 1 0 seconds although if slight siftin of the chemicalcomposition is, permissible, the range can go as low as 0.1 seconds andcan go as high as 100 secondS Darticu1arly when the pad contains arelatively slow-starting and gentle-acting exothermic composition.Suitable materials may be designed or selected which will assume thedesired porosity properties under conditions of use. For example, thepresence of'fillers or sizings in the absorbent. material may decreasethe porosity of the fabric in the dry state. However, if these materialsare affected by the activating operation, the fabric may assume thedesired properties. In selecting such materials, therefore, theirporosities should be evaulated either before the filling or sizingmaterials have been added or after theyhave been removed or disrupted asby the pad activating step. Without regard to added materials, otherphysical changes in the fabric may also be induced by the ac;

tivating operation which will bring the porosity properties of theabsorbent material within the desired range. Materials that soften anddecrease in density upon treatment with. the activating solution shouldbe evaluated for porosity after these physical changes have taken place.

With the face thus constructed with careful attention to thewater-holding capacity and porosity of the fabric, a pad is providedwhich is practically foolproof when activated by a dippingtoperation asshown by the following experimen Pads each having over-all dimensions of1% by 2%inches and containing 5.5 grams of an exothermic compositionwere .dipped in water for 3%; inch-in diameter with a various lengths oftime, and the time required forthe pad to start steaming after the startof dip, the peak temperature obtained and the time thetemperatureremained above 220 F. were noted, The temperatures were measured byplacing each pad, after removal from the dipping solution and afterpressing the absorbent face of the pad against a dry absorbent surface,on an iron rod weighing 32 grams, 3 2 inches long by 4 inch holeconcentrically bored through the length of the rod for a distance of 2/2 inches. The thermometer was placed in the bore for recording thetemperature.

The following results were obtained:

Time Integval T M in econ 5 line 1n 1n- Peak Temperait ito fii? ifiiiiiiii" trembled 51f; irfitifd Start of 111 Degrees Above 200 F.Steaming sorbent pads or manipulation is necessary and the beauticiancan be assured of uniform and satisfactory performance merely by dippingthe pad. Elimination of separate absorbent pads is a great boon to theoperator, because of the time-saving involved. The usual messy pile ofwet absorbents, difficultly separated and applied to the pad, isdispensed with.

Because the pad has considerable thickness and bulk, necessary forproviding adequate waterholding capacity, diffusion of electrolytes tothe hair with resulting contamination and possible objectionablechemical action is not encountered, even though the pad is applieddirectly to the hair without interposition of a shield. Were a perforatepad or a pad having a thin imperforate face dipped, even if doneexceedingly carefully to properly control the activation, some sort ofan absorbent or equivalent material to serve as a shield would still benecessary to prevent diffusion of electrolytes directly onto the haireither through the perforations or through the thin pervious face.Furthermore the performance of the preferred pad of this invention ispractically independent of the dip interval within the commerciallydesirable range of one to ten seconds.

While cotton felt with or without a lamination of woven fabric has beendescribed as having the physical characteristics, as above defined,necessary for use in fabricating the improved pads of this invention,other absorbent fibrous sheets of a cellulosic nature may be utilized,including certain bibulous papers of similar or even less caliper downto l or 2 mils. Some such papers have all the necessary qualities exceptthat of wet-strength or water-holding capacity. If, however, theporosity of such papers falls within the preferred porosity rangeheretofore defined, wet-strength deficiency may be overcome by providinga reticulated fabric reinforcement, and inadequate water-holdingcapacity may be corrected by application of a saturated absorbentmaterial to the face with manipulation. Because of proper porosity, theamount of manipulation required is greatly reduced and ballooning isentirely eliminated.

In Fig. 4, we have shown a modified form of pad wherein the backimperforate wall has been folded over the front longitudinal marginalportions of the face material 2. This modification is sometimesdesirable in order to provide baflles 8 and 9 which protect the scalp bydirectin the egress of steam to the central unbafiled area which isfurther removed from the scalp. The effect of the bafiles is shown inFig. 5, the arrows indicating the direction of application of steamtowards the tress. For purposes of clarity a space is shown in Fig. 5between the face 2 and tress, although as hereinbefore stated, in actualuse the face 2 would be in direct contact with the tress.

In the case of the pad of Fig. 4, the adhesive material is applied inthe same manner around the edges of the pad, the baffle portions 8 and 9lying over but not being attached to the face material 2 except alongthe marginal edge portions of the pad as indicated.

We claim:

1. A chemical heating pad adapted for use in permanent waving of humanhair having at least a portion of one face thereof formed of animperforate but moisture-pervious, absorbent sheet comprising unwoven,felted cellulosic fibers and an exothermic composition contained withinsaid pad beneath and contacting said sheet, said sheet having a moistureabsorbency and retentivity such that when immersed in water at F. for 10seconds and allowed to drain for 10 seconds at 70 F., it retains anamount of absorbed water at least equal to 0.2 grams per square inch andsaid sheet, when free of contained water-soluble materials, having aporosity as defined in the accompanying specification of 0.1 to 10seconds.

2. A chemical heating pad as claimed in claim 1 wherein said sheetconsists essentially of cotton fibers.

3. A chemical heating pad as claimed in claim 1 wherein the saidporosity is about 0.5 to 10 seconds.

MORRIS J ROOT. RAYMOND E. REED.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

